Fluid distribution and distributor



June so, 1959 I RM HI K 2,892,262

FLUID DISTRIBUTION AND DISTRIBUTOR Filed... Sept. 23, 1957 o :3 o :3 Q o 0 2 0 0 o Q INVENTOR.

RafierfM J'fizrk Q 4770mm.

United States Patent 2,892,262 FLUID DISTRIBUTION AND DISTRIBUTOR Robert M. Shirk, Wilmington, Ba, assignor to Houdry Process Corporation, Wilmington, Del., a corporation of Delaware Application September 23, 1957, Serial No. 685,673

5 Claims. (Cl. 34-57) This invention is concerned with the distribution of large volumes of compressible fluids, such as gases and vapors, in confined regions containing particulate solids. More particularly it is concerned with the provision of means and techniques whereby the high velocities of the fluids thus introduced are reduced to below the velocity at which disturbance of the solids in a bed or layer thereof would be ellected.

The introduction of compressible'fluids into enclosed vessels and the like has encountered many problems, and attempts at their solution have been made more or less successfully with a legion of introduction devices including nozzles, lances, open-ended pipes, channels, manifolds, and so on. In the realm of hydrocarbon processing operations, particularly, large volumes of gases and vapors are processed under a wide range of-conditions in variously formed vessels to achieve results such as the preparation of high quality gasoline and/ or specific chemicals, either per se or as separable components in mixed product. The efiective use of catalysts for promoting various hydrocarbon reactionsis well established, and a high percentage of hydrocarbon processing is eflected Patented June 30, 1959 'ice The problem arising in connection with an operation j of this sort is that very large volumes of vapors are desirably introduced into a relatively small space under conditions resulting in turbulent fluid flow. Uncontrolled or not suitably positioned introduction of the large fluid volumes may resultin velocities at one or more regions within the introduction area such that at times violent sition to lesser extent but still to a degree not only interfering with the proper conduct of the reaction, but also having detrimental eifect on the catalyst and equipment through abrasion, attrition and the like. In order to overcome this problem, the available forms of introduction were considered and found unsuitable for one or more reasons.

While certain estimations and calculations of expected gas velocities are possible in connection with flow through pipes, orifices and the like on the basis of known fundain the presence of such catalysts which may have physical form generally ranging from very minute particles to coarse granules or pellets which have dimensions generally in the range of about to A inch in diameter. Some of the hydrocarbon reactions are efiected in the presence of mixed sized ranges of generally minute particles maintained at a pseudo liquid.conditionidentified in theart as fluid operations. The present invention is directed more particularly to catalytic operations employing the generally larger sized particles such as those in the range of to V2 inch in diameter which'are maintained in a relatively compact bed of fixed position within a reaction vessel "and wherein such fixed position is to be maintained without substantially disrupting or dislodging the particles of solid throughout the, course of the reaction or reactions taking place in the presence thereof. a

While it should be understood that no :limitation is to be placed on the invention because of the description in connection with a specifictype operation, the description will be in terms of a knowncatalytic operation in which gasolines and naphthas are reformed to improve their motor fuel value, particularly the octane ratings, in the presence of commercially available catalyst comprising a minor amount of platinum supported on alumina and having dimensions in the order of aboutg to. 3 4 inch. It has been found that under the proper selected operating conditions, such catalyst is quite effective in promoting the desired reaction, and that large volumes of the vaporized hydrocarbons can be processed over relatively small amounts of catalyst. In the interest of economies, the quantity of this expensive catalyst necessary to effect the desired reaction is held to a minimum and the reaction vessel utilized for these reactions .is

"ment as is reasonably feasible.

mentals of fluid dynamics, theoretical analysis of velocity distribution as a result of introduction of turbulent streams of :gas from a conduit into a confined space containing gasv at rest or in motion presents considerable difiiculty. Calculations on a strictly mathematical basis have proved unreliable because of the unavailability of fundamental data on many of the encountered situations and because of accompanying changes in the characteristicsof the fluid as a result of variations and changes during flow. Changes in the temperature, pressure, density and viscosity, besides those due to any chemical transformations that may have taken place in transit have marked effect on the velocity. For these reasons, despite continuing investigation and development of fundamental data to serve as a basis of determining expected behaviour of the flowing gas under numerous encountered conditions, high safety factors are still being introduced by way of costly overdesign of equipment for fluid distribution; or, at times, hit or miss predictions based on empirical experience in other situations thought to be parallel have resulted in the construction of inadequately designed systems. While the investigation of new situations in prototype models and pilot plants would reduce the elements of chance design, such investigation is quite costly and cannot be afforded in all instances from the standpoint of time and expense involved. I As a result of extensive independent studies and observations of fluid behavior to supplement the fundamental information available in prior literature to the extent found reliable, there is provided by the present invention a novel method for handling large volumes of gases and vapors introduced into a treating vessel containing a fixed bed of granular solids enabling the use of adequate equipment at economic construction costs. In accordance with this invention, introduction of a large volume of compressible fluid within a confined resigned to provide a total effective discharge area greater than the area of the inlet to the vessel. The total distance of any one discharge port from the nearest reflecting surface is at least seven'times the diameter of the port, to overcome the effect of sustained axial velocity as hereinafter explained. In this manner the maximum fluid velocity is so reduced in a magnitude that the portion of the fluid flowing at or into the surface of the bed is maintained below a critical value represented by the formula:

vd=7ls2 Where:

V =velocity in feet per second-disturbance velocity. D =diameter of particles in feet.

=p"article density in pounds per cubic feet. 7 =gas density in pounds per cubic foot at flowing T. and P.

The reduction of fluid velocity as a result of increased flow area is well understood in that at any given volumetric flow rate the average linear velocity of the fluid flowing through a confinedpath is inversely proportional to the area of the path. In the description, however, reference is made to the effective discharge area. This designation takes into consideration the coefficient of contraction of the fluid stream passing through an orifice to provide a vena contracta beyond the orifice. As a re= sult of such stream contraction, the average velocity, and more importantly the velocity at the axis of the stream, is greater than that calculated on the basis of considering the actual diameter of the port. To overcome the effect of such velocity increase, accordingly, the size and number of the ports in the distributing manifold is designed to provide a total efliux area of not less than 1.7 times that of the vessel inlet, and preferably, in the case of inlet gas velocities approaching or exceeding 100 feet per second at the inlet, the total discharge area of the ports in the manifold should be 2 to 3 times that of the inlet.

Reference has been made above to the axial velocity of the fluid stream discharged from a port or orifice as distinguished from the average velocity of such stream; A stream of gas discharged into a large area through con fining conduit or port forms a jet having free turbulence characterized by eddies which move at different velocities. The jet can be considered as subdivided into three regions according to the axial distance from the discharge port, which are termed: the potential cone region, the transition region and the developed flow region. The potential con'e region is the cone shaped zone having an apex above the discharge port,- in which region the fluid velocity re= mains equal to the original velocity at the discharge port. The surface of this potential cone represents the limit to which mixing has penetrated into the original fluid stream and the tip of the cone represents the point at which turbulent mixing has reached the .axis of the fluid jet. The apex of this cone has been found experimentally to lie at a distance from the discharge port'of approximately .4 times the diameter of the port. In the mixing region surrounding the cone of undiminished fluid velocity,- there is a loss in the linear velocity component with increase of distance from the port. 7 V p p In the developed flow region, some distance beyond the apex of the cone turbulent mixing has reached an asymptotic state. Here radial velocity profiles and the velocity distribution at the axis can be reliably ascertained by relatively simple theoretical treatment. In the transition region between the apex of the cone and the beginning of the developed flow region the velocity distribution is changing from the characteristics of the potential cone region to those prevailing in the developed flow region. No theoretical treatment applicable to this transition region has been fully developed.

This transition region has been found to extend for a distance beyond the cone region of 7 to 8 diameters from the discharge port. To arrive at a reasonably reliable basis for estimation of the rate of velocity decline of the fluid stream, the discharge ports in the manifold are located at a distance from the reflecting (or deflecting) surface nearest thereto such that in flow from such surface there obtains the characteristic velocity decline of fluid flow in the developed flow region. The rate of such in which:

U =fluid velocity at the axis of the stream at any point on said axis,

T7 is the average discharge velocity of the stream at the port,

x is the axial distance from the discharge port to such Pa t nd 7 D is the diameter of the port.

Applying the above formula and as confirmed by experimental results, the rate of approximate decline of velocity. (at the axis of the stream) will be seen from the following tabulation:

Thus, itis seen that in flowing from the discharge port toward a reflecting surface the gas stream has about reached or has. entered into the fully developed flow region so that its maximum velocity has been reduced by atlea'st 10 to 15%. In flowing from such surface to the bed the fluid stream in addition to some velocity loss depending on the angle of impact, loses velocity at the characteristic rate for the developed flow region in following an unobstructed path permitting association and mixing with vapors in the surrounding atmosphere at all portions of the periphery of the stream.

Fuller understanding of the invention may be had by reference to the following description and claims taken in connection with the accompanying drawing forming a part of this application in which:

Fig. 1 is a cross sectional view of a spherical reaction vessel-incorporating a distribution manifold of the type contemplated by the invention;

Fig. 2 is a plan view of the distribution manifold taken at line 2 2 in Fig. 1;

Fig. 3 is a plan view of an enlarged segment of the distributingv member shown in Fig. 2;

Fig. 4 is. a cross sectional elevation taken at line 4-4 on Fig. 3;

Fig. 5 is a plan view of a modified distributing manifold embodiment; and

Fig. 6 is a cross sectional elevation taken at line 6-6 on Fig. 5.

Referring to Fig. 1, there is shown a spherical reactor vesselll having an internal diameter of approximately 10 /2 feet. Horizontally positioned within and spaced apart from the bottom area of vessel 11 is a grating suptional 4 inch layer 16 of inch diameter alumina spheresgiving a bed surface of about 56.7 square feet and leaving approximately 237 cubic feet of space, above the bd surface, as the confined region into which the charge gas is introduced.

It is to be understood that the description is of an embediment of a particular operation and is not indicated to belimiting in substances, quantities or measurements. Forinstance, the size and'distribution of the alumina spheres may vary as may the size of the catalyst bed as wellas the type of catalyst. As will be noted hereinafter, the size and shape of the reaction vessel and the interior therefore may likewise be varied to suit con ditions and design classification.

Horizontally positioned above and spaced apart from the upper layer of alumina spheres 16 is gas distributing manifold 17 supported in an axial position by feed member 18 and strap 19. Strap 19, in turn is fastened to manway 21 which is normally closed by seal plate 22. Manway 21 may be used for access to the interior of vessel 11 when necessary.

, In the lower region of vessel 11 a suitable solids discharge pipe 23 is in direct communication with the portion of the reactor vessel above supporting grating 12. Pipe member 23 is sealed by means not shown to prevent passage of solids or gases during operation. Around the centrally positioned vertically extending pipe member 23 is a gas removal conduit 24 in open communication at its upper end with the plenum 26 existing between the lower part ofvessel 11 and supporting grating 12. The gas discharge conduit 24 discharges into suitable transfer members, not shown, and serves as the means through which reaction products are recovered. Grating 12 is supported peripherally by the walls of vessel 11 and interiorly by support members 27.

In the normal operation of a reactor, as herein described, for the reforming of a gasoline boiling range charge stock, it has been found, for the desired quantity of charge introduced through a nozzle of approximately 18" I.D., the gas discharges from the feed member or nozzle 18 at approximately 100 ft./ sec. and has a velocity at the surface of the bed in the range of at least 65-70 ft./sec. At such high gas velocity there is considerable and violent disturbance and disruption of the solids in the bed, with attendant breakage of the catalyst, erosion of equipment, and a rapid increase in the pressure drop through the catalyst bed because of an accumulation of the broken catalyst particles in the bed. It was found further that when a trough-like deflection member was positioned between the nozzle and the bed surface to prevent direct access of the incoming gas stream to the surface of the bed the gas velocities at the surface of the bed were still in the order of 45-50 ft./sec. at portions of the bed surface. At these velocities and in accordance with the previously described formula, an appreciable amount of churning and moving of solids particles in the upper portion of the bed resulted in appreciable breakage and attrition with unsatisfactory gas flows through the bed of catalyst. In order to obtain a practical operating gas velocity, gas distribution member 17, as shown more fully in Figs. 2, 3 and 4, was installed and serviced by nozzle 18.

With the reactor system described in connection with Fig. l, the highest permissible gas velocity as determined through application of the above-described formula at the surface of the bed could not be greater than 28 ft./sec. With the gas distribution through gas distribution member 17, constructed as hereinafter described, the gas velocities at the bed surface were uniformly in the range of about 18 23 ft./sec. and thus Well within the safe operating limit.

Referring now particularly to Fig. 2, gas distribution member 17 is shown as a hexagonal ring type member served by nozzle 18 and discharging gas therefrom through one inch ports positioned in the upper 120 of the five segments exclusive of the segment in which gas nozzle 18 is attached. Avoiding discharge from the segment in which the main gas stream is introduced provides for better distribution of the gas in the manifold and insures more nearly equal gas flow to the ports in the other segments. The general distribution and location of the of the discharge ports is such that the distance therefrom to the nearest reflecting surface, tag, the upper wall of vessel 11, is greater than seven times the diameter of any individual port; that is, for these 1 inch ports no one of these is at a distance of less than 7+ inches from the nearest reflecting surface.

In the particular system described, direct introduction of the required gas volume resulted in a gas velocity at the discharge end of nozzle 18 in the order of feet per second through an effective discharge opening of approximately 254.5 square inches. The jet eifect of the incoming gas continued with only minor exterior decay (to about 70 feet per second average velocity) at the surface of the beda travel distance of about2 /z feet and substantially less than seven or more times the diameter of nozzle 18.

The introduction of a baffle between-the opening of nozzle 18 and the bed surface in such manner as to redirect the incoming jet away from direct contact with the bed surface without changing the effective dischargerate of the nozzle efiected some reduction in the velocity of the gas reaching the bed surface; however, this velocity, averaging about 50 feet per second, was still far too high for successful operation.

.With the attachment of manifold 17 to nozzle 18 there was still no material effect on the velocityof the gas emerging from nozzle 18 into manifold 17. Now, however, this gas introduced into manifold 17 is redirected and discharged through 585 ports or nozzle openings 28 having a total effective opening area of approximately 459 square inches, almost double that of nozzle 18. In

addition, each of the openings 28 is so positioned as to discharge gas flowing therethrough in a direction away from the surface of the bed. In further consideration it is seen that the jet effect of the individual gas stream is successfully dissipated in that the distance of travel to the wall of every single gas jet passing through openings 28 is generally greater than seven times the effective opening (one inch diameter) of each of openings 28. As a result of this method of gas introduction, the velocity of the gas at the bed surface was in the order of 20 feet per second and thus well below the allowable upper limit of about 28 feet per second for the particular system herein described.

The positioning of the discharge ports such that the gas passing therethrough is directed toward a wall surface or surface other than the surface of the bed of particles thus gives an added measure of protection against unduly high local velocities at the bed surface. As previously stated the positioning is such as to permit the full decay of the individual jet effect at or before reaching a wall surface, and even with a malfunctioning jet stream not fully dissipated before reaching the wall such a jet still has the return distance either along an expanding path due to wall curvature or through space to permit loss of any jet elfect with concomitant velocity decrease to an acceptable average value prior to reaching the bed surface.

The embodiment set forth in Figs. 1 through 5 contemplates a specific reaction system. As previously indicated, reasonable deviations are within the scope of this invention. For example, a cylindrical vessel horizontally positioned is suitably used in connection with a gas distributor nozzle system shown in Figs. 5 and 6 wherein a centrally located inlet line 31 feeds into spider member 32 which in turn discharges relatively uniformly into gas distribution member 33. Member 33 has gas distribution ports positioned in the upper half thereof for discharge into the upper region of the reactor vessel in accordance with the requirements of size and number of openings, travel distance and the like to give velocity in accordance with the foregoing description. Other nozzle forms and gas distribution member forms, such as 7 square, circular-or other, are likewise within the scope of is f v i l a Ob iy may modifications and variations of the p'r'esrit invention as hereinbefojr'e 'setforth may be made without depa'rtiiig from the spirit andfs'cope thereof and therefore only Such limitations 'sl'lo'uld be imposed as are indicated in the appended Claims.

I claim: I

, 1. In afr'e'ac'tor' vessel containing a fixed bed of grainular material extenclirfg throughoiit an intermediate level therein and being spaced from its upper end so as to provide therewith a plenum having the surface of said bed as its lowermost boundary, a gas feed nozzle Communieating with "said plenu and gas withdrawal means at the bottom of said bed, the configuration and size of said plenum and the location and size of said gas feed nozzle Beifig that for desig input of gaseous material through said nozzle the velocity of gas flowing directly therefrom to said surfaee of the bed would exceed the bed-disturbing velocity (Va), as determined by the forwherein D is the average'diameter of solid particles in said bed, p the particle density and p; is the density of the fluid the combination therewith of: a gas distributor comprising a horizontal manifold conduit supported with in said plenum and above the surface of said bed, said manifold Conduit having a plurality of upwardly directed ports whose total discharge area exceeds the discharge area of said gas feed nozzle in the ratio of at least 1.7

to 1 and each of said ports being spacedlfrom the lenum anieter of the 'por't; the size, number and arrangement of said ports h'e'ihg' such as to substantially reduce the veloc':-' ity of the incoming gas stream whereby the velocity of the gas at all points on the surface of said bed will be less than said bed-disturbing velocity.

2. Apparatus as in claim 1 in which the total discharge area of said port's ekce'e'd's the discharge area of said gas feed nozzle in the ratio of between 1.7:1 and 3:1.

3. Apparatus as in claim 1 in which said distributor has a region of free flow area greater than the discharge area of said gas fed nozzle.

4. Apparatus as in claim 1 in which said distributor comprises a circumfer'entially complete tubular member having an inlet connector communicating with said feed nozzle, and being provided along its entire up'per curv'e surface with uniformly spaced ports, the axis or dis'charge' of said ports being directed toward the upper end walls of said vessel.

5. Apparatus as in claim 4 in which the configuration of the continuous tubular inernb'er conforms in general to the surface outline of the bed, so that all portions of the tubular member may service substantially equal portions of the bed.

References Cited in the file of this patent UNITED STATES PATENTS Houdry Aug. 29, 1950 

